JP3288523B2 - Light spot position measuring device and light spot position measuring method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light spot position measuring apparatus and a light spot position measuring method for measuring the position of one or a plurality of point light sources which emit light directly or indirectly using an image pickup device. About. More specifically, the present invention relates to a technique for improving the accuracy of such light spot position measurement.

[0002]

2. Description of the Related Art Conventionally, for example, when measuring the shape of a three-dimensional object, the object to be measured is irradiated with a laser beam using a scanning laser projector, and a laser spot generated on the object is imaged by two television cameras. The stereo method has been implemented. An image signal output from each television camera is arithmetically processed to determine a three-dimensional position of each spot. The surface shape of the three-dimensional object is measured by sequentially performing scanning of the laser spot along the surface of the measured object and measurement of the three-dimensional coordinates in synchronization with each other. In order to improve the measurement accuracy in such a measurement system, it is necessary to improve the resolution of the television camera. However, for this purpose, the number of pixels of an imaging device such as a CCD image sensor incorporated in a television camera must be greatly increased, but this is difficult in terms of manufacturing technology.

[0003] Techniques for improving apparent resolution without increasing the number of pixels of an imaging device have been proposed.
For example, this is disclosed in Japanese Patent Publication No. 3-31362.
According to this, a cross filter is attached to an objective lens of a television camera, a light beam from a target light point is converted into a streak cross-shaped image by the cross filter, and is projected on a light receiving surface of an imaging device. This projection image is image-processed, and the intersection of the cross-shaped image is calculated in sub-pixel units to determine the position of the point light source forming each target.

[0004]

However, such a conventional technique has a disadvantage that a light source emitting strong light must be used in order to increase the accuracy of detecting the position of a light spot. In the cross-shaped streak image converted by the cross filter, the power of the main light is concentrated at the center, and the power of the light dispersed in the periphery is insignificant. For this reason, the light power is not used effectively. As a result, in order to improve the accuracy of position detection, the power of light emitted from the light spot must be increased. In other words, if the light from the light spot is not strong to some extent, the streak-shaped cross-shaped image cannot be projected clearly, resulting in a disadvantage that the sensitivity is poor. Due to such disadvantages, in the above-described three-dimensional object shape measurement and the like, there are restrictions on the distance from the television camera to the object to be measured and restrictions on the reflectance of the object surface, and the application field is naturally limited, for example, This has made application to civil engineering surveys difficult.

[0005]

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the prior art, an object of the present invention is to enable high-accuracy position measurement even at a light spot that emits weak light. The following measures were taken to achieve this purpose. That is, the intersection position measuring device according to the present invention includes an optical conversion unit, an imaging unit, and an image processing operation unit as a basic configuration.
The optical conversion means condenses light emitted from a light spot included in the measured object and converts the light into a plurality of linear images crossing each other.
The imaging means receives the linear image and outputs corresponding image data. The image processing operation means processes the image data, extracts a plurality of corresponding straight lines from the plurality of linear images, calculates an intersection thereof to determine the position of the light spot. In such a configuration, the optical conversion means has a plurality of cylindrical lens surfaces, and each of the cylindrical axes intersects each other to generate the plurality of linear images. For example, the optical conversion means has a pair of cylindrical lens surfaces, and respective cylindrical axes are orthogonal to each other to generate a cross-shaped linear image. The pair of cylindrical surfaces are formed in one lens, and each cylindrical lens surface is divided into multiple parts symmetrically with respect to the optical axis of the lens.

The light spot position measuring method according to the present invention comprises a conversion procedure, an imaging procedure, and a calculation procedure. In the conversion procedure, light emitted from a light spot included in the object to be measured is condensed using optical conversion means having a plurality of cylindrical lens surfaces having cylindrical axes intersecting each other, and a plurality of linear Convert to image. Next, in the imaging procedure, a linear image is received using the imaging means, and corresponding image data is output. Finally, in the calculation procedure, the image data is processed using the image processing calculation means, a plurality of straight lines are extracted, and their intersections are calculated to determine the position of the light spot.

[0007]

According to the present invention, for example, a lens having a pair of cylindrical lens surfaces whose cylindrical axes are orthogonal to each other is added to or used as an objective lens of a television camera to constitute an optical conversion means. . Thereby, the light emitted from the light spot can be converted into a cross-shaped linear image orthogonal to each other. Unlike the conversion using the conventional cross filter, the conversion using the orthogonal cylindrical lens surface makes it possible to uniformly disperse the light power emitted from the light spot toward the periphery and form the outline of the linear image sharply. is there. By performing image processing on a cross-shaped linear image having a considerable luminance and a sharp outline, the intersection of the orthogonal straight lines can be determined very precisely in the order of sub-pixels. Therefore, even if the light power generated by the light spot is weak, the entire amount of light is effectively used, and the position of the light spot can be stably measured with extremely high accuracy. In a three-dimensional object shape measurement system or the like that performs spot scanning with a laser beam, it is possible to extend the measurable distance and to compensate for a decrease in sensitivity due to an increase in the speed of laser scanning.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram showing a first embodiment of the light spot position measuring device according to the present invention. This apparatus is a television camera 1 and an image processing and arithmetic unit 2 comprising a computer and the like.
And The television camera 1 captures an image of the light spot 3 included in the measured object. The image processing arithmetic unit 2 processes the image captured by the television camera 1 and outputs information indicating the light spot position. The objective lens 4 of the television camera 1 is provided with a cylindrical lens 5 and constitutes an optical conversion means. The cylindrical lens 5 has a plurality of cylindrical lens surfaces, and the respective cylindrical axes intersect each other. In this example, the cylindrical lens 5 has a pair of concave surfaces of the cylindrical lens, and the respective cylindrical axes are orthogonal to each other. The optical conversion means including the objective lens 4 and the cylindrical lens 5 condenses the light emitted from the light spot 3 and converts the light into a plurality of linear images intersecting each other. In this example, the images are converted into cross-shaped linear images that are orthogonal to each other. The television camera 1 incorporates, for example, a CCD image sensor 6 as an image pickup means, receives a cross-shaped linear image 7, and outputs corresponding image data. The image processing calculator 2 processes the image data to extract a pair of corresponding straight lines from the cross-shaped linear image 7, and calculates the intersection to determine the position of the light spot 3.

FIG. 2 is a schematic perspective view showing a specific configuration example of the cylindrical lens 5 shown in FIG. As described above, the cylindrical lens 5 has the pair of cylindrical lens surfaces A and B, and each of the cylindrical axes C
A and CB are orthogonal to each other. The intersection of the cylindrical axes CA and CB is located on the optical axis passing through the center O of the lens 5. One cylindrical lens surface A is divided into two symmetrically with respect to the optical axis of the lens 5. The other cylindrical lens surface B is also divided into two symmetrically with respect to the optical axis. Therefore, the cylindrical lens 5 has a point-symmetric surface shape.

FIG. 3 is a schematic diagram showing an end face shape of the cylindrical lens 5 shown in FIG. As shown
When observed from the direction of the cylindrical axis CA, a concave shape of the cylindrical lens surface A appears. Further, when observed from the direction of the cylindrical axis CB, a concave shape of the cylindrical lens surface B is recognized. When a lens 5 having a pair of orthogonal cylindrical lens surfaces A and B is added to the objective lens 4 (FIG. 1), the light flux from the light spot 3 to be focused by the objective lens 4 is changed according to the passing area of the lens surface. Divided. Since each of the two divided light beams passes through the orthogonal cylindrical lens surfaces A and B, they are formed as a cross-shaped linear image. This is because a light beam to be focused as a point is diverged in a direction orthogonal to the cylindrical axis of the cylindrical lens surface. In this example, a concave cylindrical lens surface is employed, but from the viewpoint of the diverging function, a convex cylindrical lens surface may be used. By interposing the cylindrical lens surface in this manner, the light power of the light spot 3 can be uniformly dispersed toward the periphery, and a sharp linear image can be generated. In particular, FIG.
The cylindrical lens 5 shown in (1) has an axially symmetric surface shape, can uniformly disperse the light power in four directions, and can obtain a cross-shaped image having a well-defined shape.

FIG. 4 is an explanatory view showing a method of manufacturing the polygonal cylindrical concave lens 5 shown in FIG. As shown in (A), a rotary drum provided with a polished surface is pressed against the surface of the optical glass and rotationally polished to form one cylindrical concave lens surface. The cylindrical axis of the cylindrical lens surface thus obtained coincides with the rotation axis of the rotary drum. Next, as shown in FIG.
In the rotating state, the rotating drum is pressed again to form a concave surface of the other cylindrical lens. In this example, the cylindrical concave lens 5 having two surfaces and four divisions is formed by a polishing method, but may be formed by an injection molding method instead.

Next, an example of an image processing operation procedure will be described in detail with reference to FIG. As shown in (A), an orthogonal coordinate system (X, Y) is set so as to match the cross-shaped linear image 7 projected on the CCD image sensor. Next, as shown in (B), the area value of the cross shape projected in the X-axis direction is calculated. The histogram curve thus obtained is differentiated. The results are shown in (C). X coordinate values x1 and x2 corresponding to the maximum value and the minimum value of the differential curve are obtained, respectively.
Using the image data included in the band area defined by x1 and x2, a linear image in the Y-axis direction is approximated by a straight line using the least squares method, and a corresponding straight line is extracted. By a similar process, a straight line corresponding to a linear image along the X direction is extracted by the least square method. The intersection of a pair of straight lines is calculated to determine the position of the light spot.

FIG. 6 is a schematic perspective view showing a second embodiment of the light spot position measuring device according to the present invention. Light spot 3 and CC
A convex lens 40 and a compound cylindrical lens 50 are interposed between the D image sensor 6 and constitute an optical conversion unit. The convex lens 40 corresponds to the objective lens 4 shown in FIG. 1, and focuses the light emitted from the light spot 3 on the CCD image sensor 6. Compound cylindrical lens 5
0 is a substantially triangular cylindrical convex lens 51 and 52
Are bonded together. One cylindrical convex lens 51 has a vertical cylindrical axis, passes half of the converged light, and diverges in the horizontal direction. The other cylindrical convex lens 52 has a horizontal cylindrical axis, and diverges the remaining half of the focused light in the vertical direction. As a result, a cross-shaped linear image 7 is projected on the CCD image sensor 6. Composite cylindrical lens 5 used in this example
0 denotes a two-sided, four-part cylindrical concave lens 5 shown in FIG.
Although it is not point symmetric as in the above, it can be created relatively easily.

FIG. 7 is an explanatory diagram showing an example of a method for producing the composite cylindrical lens 50 shown in FIG. In this example, a long cylindrical lens is first cut along a cut line 53 perpendicular to the cylindrical axis. One of the cuts is further cut along the oblique cut line 54 to obtain triangular cylindrical lenses 52 and 55. The other is cut along the oblique cut line 56 to obtain a pair of triangular cylindrical lenses 51 and 57. When the cylindrical lenses 51 and 52 having a triangular shape processed in this manner are joined via a cut surface,
The composite cylindrical lens 50 shown in FIG. 6 is obtained.

FIG. 8 is a schematic view showing a third embodiment of the light spot position measuring device according to the present invention. In this example, light spot 3 and CC
A two-surface four-part cylindrical convex lens 500 intervenes with the D image sensor 6. The cylindrical convex lens 500 also serves as an objective lens, and independently constitutes an optical conversion unit. When a lens having two cylindrical surfaces is used as an objective lens, each cylindrical surface needs to be convex. The cross section of the cylindrical convex surface perpendicular to the cylindrical axis has the same function as the spherical convex lens, and the image of the light spot 3 is focused according to the lens formula. On the other hand, since the section of the cylindrical convex surface along the cylindrical axis is rectangular, light emitted from the light spot does not converge. That is, the cylindrical convex lens can convert and project a light spot into a linear image independently without combining with a spherical convex lens. In the two-sided, four-split cylindrical convex lens 500 having a pair of cylindrical convex surfaces whose respective cylindrical axes are perpendicular to each other, the light flux along the optical axis is divided into two in accordance with the passing area, and the two divided light fluxes are orthogonal lines. An image is formed as a shape image. In general, such a lens can generate an arbitrary number of linear images along an arbitrary direction according to the number of surface divisions and the number of cylindrical convex surfaces assigned to each divided surface.

Referring to FIG. 9, an example of a method for producing the two-surface four-part cylindrical convex lens 500 shown in FIG. 7 will be described. In this example, a cylindrical convex lens is formed using a mold. The mold is processed in the same manner as the method shown in FIG. 4, and orthogonal polishing using a rotating drum is performed. It should be noted that the forming method is not limited to this, and a two-surface four-part cylindrical convex lens may be formed by direct polishing.

FIG. 10 is a schematic diagram for explaining the operation of a cylindrical convex lens having the function of an objective lens. The cross section orthogonal to the cylindrical axis of the cylindrical convex lens 501 has a convex shape, and the light beam emitted from the light spot 3 is focused according to the lens formula. On the other hand, since the cross section of the cylindrical convex lens 501 along the cylindrical axis is rectangular, it does not converge at all. As a result, a linear image 701 parallel to the cylindrical axis is projected on the CCD image sensor 6.

FIG. 11 is a schematic block diagram showing a fourth embodiment of the light spot position measuring device according to the present invention. In the first to third embodiments described above, the orthogonal cylindrical surface is formed in a surface-divided manner using a single lens. On the other hand, in this example, a cross-shaped linear image is synthesized using a pair of cylindrical lenses separated from each other. As shown, the light beam emitted from the light spot 3 is split into two light beams by a half mirror or a beam splitter (not shown). One optical path has a cylindrical lens 5
There is an optical conversion means including an optical lens 0A and an objective lens 40A. The cylindrical lens 50A has a vertical cylindrical axis, and projects a horizontal linear image 7A on the surface of the CCD image sensor 6. In the other optical path, an optical conversion unit including a cylindrical lens 50B and an objective lens 40B is interposed. The cylindrical lens 50B has a horizontal cylindrical axis, and projects a vertical linear image 7B on the surface of the CCD image sensor 6. Linear images 7 orthogonal to each other
A and 7B are combined via an optical system (not shown) to generate a cross-shaped linear image 7.

FIG. 12 is a diagram for explaining the operation of the optical conversion means comprising the cylindrical lens 50A and the objective lens 40A shown in FIG. (A) is a cylindrical lens 5
It is a horizontal geometrical optics diagram along a plane orthogonal to the cylinder axis of OA, and (B) is a vertical geometrical optics diagram also along a plane parallel to the cylinder axis. As shown in (A), if the cylindrical lens 50A is not interposed, the light beam emitted from the light spot 3 along the optical axis is condensed by the objective lens 40A, and
A spot image is formed on the surface of the CD image sensor 6. However, actually, since the cylindrical lens 50A is interposed and refracted along the convex surface, the incident light beam is defocused and the horizontal linear image 7A is
Will be projected. On the other hand, as shown in (B), the vertical cross section of the cylindrical lens 50A has a simple plate shape and does not exhibit any refraction. Therefore, the light beam incident along the vertical section is focused at one point by the objective lens 40A.

[0020]

As described above, according to the present invention, a lens having a sharp light spot can be obtained by adding a lens having at least two cylindrical surfaces to an objective lens of a television camera or using it as an objective lens. It is converted into a linear image, and the optical power can be uniformly distributed to the periphery.
Therefore, even if the light emitted from the light spot is weak, the light can be effectively used, and the position of the light spot can be stably measured with extremely high accuracy. In a three-dimensional object shape measurement system or the like that performs spot scanning with laser light, the measurable distance can be extended, and a lack of sensitivity when speeding up laser scanning can be compensated.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of a light spot position measuring device according to the present invention.

FIG. 2 is a perspective view of a two-sided, four-part cylindrical concave lens included in the first embodiment.

FIG. 3 is a schematic diagram showing an end surface shape of a two-surface four-part cylindrical concave lens.

FIG. 4 is a process drawing showing a method for manufacturing a two-sided four-part cylindrical concave lens.

FIG. 5 is an explanatory diagram illustrating a processing procedure of the image processing arithmetic unit illustrated in FIG. 1;

FIG. 6 is a schematic perspective view showing a second embodiment of the light spot position measuring device according to the present invention.

FIG. 7 is an explanatory diagram showing a method for producing a composite cylindrical lens included in Example 2.

FIG. 8 is a schematic perspective view showing a third embodiment of the light spot position measuring device according to the present invention.

FIG. 9 is an explanatory view showing a method for manufacturing a two-sided, four-part cylindrical convex lens included in the third example.

FIG. 10 is a diagram illustrating the operation of a cylindrical convex lens.

FIG. 11 is a schematic perspective view showing a fourth embodiment of the light spot position measuring device according to the present invention.

FIG. 12 is an operation explanatory view of the cylindrical convex lens included in the fourth example.

[Explanation of symbols]

 Reference Signs List 1 TV camera 2 Image processing calculator 3 Light spot 4 Objective lens 5 Cylindrical lens 6 CCD image sensor 7 Cross-shaped linear image

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-55-74403 (JP, A) JP-A-61-163100 (JP, A) JP-A-4-225106 (JP, A) JP-A-61-163 289785 (JP, A) JP-A-60-113333 (JP, A) JP-A-4-301535 (JP, A) JP-A-5-60518 (JP, A) JP-B-3-31362 (JP, B2) (58) Field surveyed (Int. Cl. ⁷ , DB name) G01B 11/00-11/30

Claims (5)

(57) [Claims] 1. An optical conversion means for condensing light emitted from a light spot included in an object to be measured and converting the light into a plurality of linear images intersecting with each other, and receiving the linear images and corresponding image data An image processing means for processing the image data, extracting a plurality of corresponding straight lines from a plurality of linear images, calculating an intersection thereof to determine the position of the light spot, In the point position measuring device, the optical conversion means has a plurality of cylindrical lens surfaces, and each of the cylindrical axes intersects each other to generate the plurality of linear images. Point position measurement device. 2. The apparatus according to claim 1, wherein said optical conversion means has a pair of cylindrical lens surfaces, and respective cylindrical axes are orthogonal to each other to generate a cross-shaped linear image. Light spot position measuring device. 3. The lens system according to claim 2, wherein the pair of cylindrical lens surfaces are formed in one lens, and each of the cylindrical lens surfaces is divided into multiple parts symmetrically with respect to the optical axis of the lens. Light spot position measuring device. 4. An optical conversion means having a plurality of cylindrical lens surfaces having cylindrical axes intersecting each other, condensing light emitted from a light spot included in an object to be measured,
A conversion procedure for converting into a plurality of linear images that intersect each other, an imaging procedure for receiving the linear image using an imaging unit and outputting corresponding image data, and processing the image data using an image processing operation unit A light spot position measuring method for extracting a plurality of straight lines, calculating an intersection thereof, and calculating a position of the light spot. 5. The light spot position measuring method according to claim 4, wherein the conversion step is a step of generating a cross-shaped linear image via a pair of cylindrical lens surfaces having cylindrical axes orthogonal to each other.